How to create a long shadow icon?
Using Blender Internal.

Why fake it with the power of 3d at your fingertips ;)? Although these icons have a flat style, there is still some depth to them for that realistic feel.

Add a sun lamp, adjust the angle (45+ degrees is good), set it to Ray Shadow, increase the soft size and samples, change the shadow color to a medium gray and enable ambient occlusion (use a small value). You would be surprised the control you have over the shadow. Also increase the height of the actual logo so it can cast a longer shadow. The base object needs to catch the shadow but in your example you have it set to Shadeless, if you still want that flat look, change the shader model to Fresnel. Finally set the camera to an orthographic type if you don't want the final render to be affected by perspective.